Fine powders with mean size less than 1 micron in general, and nanoscale powders with mean size less than 100 nm in particular, are a novel family of materials. A distinguishing feature of these materials is that a mean domain size is so small that size confinement effects become a significant determinant of the materials' performance. Such confinement effects can, therefore, lead to a wide range of commercially important properties. For example:
enhancement in mechanical properties, such as strengths and hardness; PA1 unique optical properties, when a domain size is less than the wavelength of visible light; PA1 unique electrical and electrochemical properties, when the interfacial atoms are a significant percentage of all atoms, and a domain dimension is less than the mean free path of electrons or holes, skin depth, Debye length, electron cloud thickness, or other physical parameters; PA1 unique electronic properties such as coulomb blockade; PA1 unique thermal properties, when a domain dimension is less than phonon length, and the interfacial processes are significant contributor to the overall properties; PA1 unique chemical properties, such as enhanced solubilities leading to non-equilibrium compositions, metastable states, and isotropic crystals; PA1 unique magnetic properties when a material's domain dimension is less than the magnetic domain size; and PA1 unique manufacturing properties, such as low temperature faster sintering of ceramics, metals, composites and alloys, and superplastic forming. PA1 The precursor raw materials for the process and method should be low-cost, safe, readily available, and environmentally benign; PA1 The compositions should be easily tailored to specific needs of the ultimate application; PA1 It should be possible to synthesize and control the composition of final powder characteristics; and PA1 It should be possible to collect the synthesized material without damage or loss of material.
Fine powders in general, and nanoscale powders in particular, therefore, represent an extraordinary opportunity for design, development and commercialization of a wide range of applications in structural, electrochemical, electrical, optical, electronics, magnetic, chemical products, and combinations thereof. Furthermore, since they represent a whole new family of material precursors where conventional coarse-grain physiochemical mechanisms are not applicable, these materials offer unique combinations of properties that can enable novel and multifunctional components of unmatched performance.
Previous patents teach the importance of fine powders and they also teach the art of producing a wide range of these powders (See, for example, U.S. Pat. Nos. 5,486,675; 5,447,708; 5,407,458; 5,219,804; 5,194,128; and 5,064,464, all of which are incorporated herein by reference). The teachings in these patents attest to the importance of these powders, yet they do not offer a method or process for high volume, low-cost production of fine powders in general and nanoscale powders of complex compositions in particular. There are several characteristics that need to be achieved in a practical commercial process:
No currently available production method has all these characteristics.